The present disclosure relates to a multilayer ceramic electronic part to be embedded in a board and a printed circuit board having the multilayer ceramic electronic part embedded therein.
In accordance with high densification and high integration of an electronic circuit, a printed circuit board lacks a space for passive components to be mounted thereon. To solve this problem, an attempt to embed parts in the board, that is, to provide embedded devices, has been conducted. Particularly, various methods of embedding a multilayer ceramic electronic part used as a capacitive part in a board have been suggested.
As methods of providing a multilayer ceramic electronic part within a board, there is provided a method of using a board material itself as a dielectric material for a multilayer ceramic electronic part and using copper wiring, or the like as an electrode for a multilayer ceramic electronic part. Further, as other methods of implementing an embedded multilayer ceramic electronic part, there are provided a method of forming an embedded multilayer ceramic electronic part by forming a high-K polymer sheet or a dielectric thin film in a board, a method of embedding a multilayer ceramic electronic part in a board, and the like.
In general, a multilayer ceramic electronic part includes a plurality of dielectric layers formed of a ceramic material and internal electrodes inserted between the plurality of dielectric layers. Such a multilayer ceramic electronic part is disposed within a board, whereby an embedded multilayer ceramic electronic part having high capacitance may be implemented.
In order to manufacture a printed circuit board having a multilayer ceramic electronic part to be embedded therein, the multilayer ceramic electronic part is inserted into a core substrate and then via holes need to be formed in an upper plate and a lower plate using a laser to connect board wirings to external electrodes of the multilayer ceramic electronic part. Such laser processing is a factor in significantly increasing manufacturing costs of the printed circuit board.
Meanwhile, since the multilayer ceramic electronic part needs to be embedded in a core portion of the board, a nickel/tin (Ni/Sn) plating layer does not need to be formed on the external electrodes, unlike a general multilayer ceramic electronic part mounted on a surface of the board.
That is, since the external electrodes of the embedded multilayer ceramic electronic part are electrically connected to a circuit in the board through vias made of copper (Cu), a copper (Cu) layer, instead of the nickel/tin (Ni/Sn) layer, is required to be formed on the external electrodes.
Typically, since the external electrode is made of copper (Cu) as a main component but also includes glass, the glass component absorbs the laser during laser processing for forming the via in the board, and thus, it may be difficult to adjust a depth of the via.
For this reason, the copper (Cu) plating layer has been separately formed on the external electrodes of the embedded multilayer ceramic electronic part.
However, due to the separately formed copper (Cu) plating layer, manufacturing costs may be increased, and due to the permeation of a plating solution, a reliability problem may still occur. Therefore, the above problems still need to be solved.
Meanwhile, an embedded-type multilayer ceramic electronic part is embedded in a printed circuit board used in a memory card, a PC main board, and a variety of RF modules, whereby the size of a product may be significantly decreased as compared to a surface mounting-type multilayer ceramic electronic part.
In addition, since the embedded multilayer ceramic electronic part may be disposed to be very adjacent to an input terminal of an active component such as a microprocessor unit (MPU), interconnect inductance caused by the length of wiring may be decreased.
An effect of decreasing the inductance in the embedded multilayer ceramic electronic part to be in the board as mentioned above is merely considered to be the decrease in the interconnect inductance obtained by an unique arrangement known as an embedded method, and is still not sufficient to improve equivalent series inductance (ESL) characteristics of the embedded multilayer ceramic electronic part itself.
In general, a current path in the embedded multilayer ceramic electronic part needs to be short in order to decrease the ESL.
However, since the copper (Cu) plating layer is separately formed on the external electrodes of the embedded multilayer ceramic electronic part, the plating solution may be permeated into the external electrode, whereby it is difficult to shorten the current path in the embedded multilayer ceramic electronic part.